Abstract
Magnesium alloy matrix composites reinforced with short alumina fibers and in-situ formed Mg2Si particles were fabricated in a permanent mold by the infiltration of magnesium alloy to the preform consisting of the fibers and attached silicon particles. Microstructures of composites and their tensile strength in the range from 293K to 623K were investigated. Phosphorus or CaF2 was applied to the in-situ Mg2Si formation as a refiner. Fine Mg2Si particles of approximately 5μm grain size were formed regardless of addition of the refiners and were homogeneously dispersed in the matrices when Si particles of 5μm were used. The strength of this composite was higher than that of the fiber-reinforced composite at every temperature measured. Examination of fracture surfaces indicated that stress transmission between the fiber and the matrix became easy owing to the particles, which reduced the fiber-to-fiber contact. The fine Mg2Si particles appear to agglomerate to each other when Si particles of 50μm were used. The strength of this composite was smaller than that of the fiber-reinforced composite.
